Despite recent improvements in diagnostic and interventional health care, mortality rates in patients with intestinal ischemia/reperfusion (I/R) remain alarmingly high, ranging from 59-93%. The long-term goal of our work involves the clinical administration of heparin-binding EGF-like growth factor (HB-EGF) to protect the intestines from injury. Our central hypothesis is that HB-EGF not only stimulates enterocytes to proliferate and to migrate, but also acts as an anti-inflammatory agent that prevents leukocyte infiltration and activation, and stimulates angiogenesis, an important component of the healing response. We base that hypothesis on multiple lines of evidence that we have accumulated demonstrating that HB-EGF protects the intestine after intestinal I/R. We have proposed three specific aims to test our hypothesis, and to allow a better understanding of the mechanistic basis of HB-EGF function, as a necessary prerequisite to developing therapeutic protocols to treat this disease. Aim [1] To test the hypothesis that HB-EGF over- or under- expression (gain or loss of function) alters resistance to intestinal I/R. We will compare the susceptibility of HB-EGF transgenic, knockout and control mice to hemorrhagic shock and resuscitation, with measured endpoints including: histologic injury grading, gut barrier function, and mortality. In addition, intestinal phenotypic changes after injury will be determined. Aim [2] To test the hypothesis that HB-EGF-mediated interference with neutrophil-endothelial cell interactions contributes to the protective effects of HB-EGF. The effect of HB-EGF on adhesion molecule expression in activated PMN and enothelial cells and the signaling pathways utilized will be determined. The effect of HB-EGF on intestinal healing in neutropenic and adhesion molecule-deficient mice will also be determined. Aim [3] To test the hypothsis that stimulation of angiogenesis contributes to the protective effects of HB-EGF. HB-EGF-mediated angiogenesis will be examined in vitro to determine the role(s) of eNOS, intracellular signaling pathways and EGF receptor subtypes. The ability of HB-EGF to stimulate angiogenesis in WT and eNOS deficient mice after intestinal injury in vivo will also be examined. The relevance of this research plan to public health will be a better understanding of the mechanisms utilized by HB-EGF in the protection of the intestines from injury after intestinal I/R, as a prerequisite for the development of HB-EGF-based therapeutic regimens.